Device and method for determining frequency and amplitude of an oscillating structure, especially for measuring acceleration or rotational rates

Apparatus for determining frequency and/or amplitude of a vibrating structure adapted for the measurement of acceleration and angular velocity comprising:

• a fixed element,
• a movable element facing said fixed element at a distance therefrom, said movable element being excited in periodic vibration about an axis of vibration in a plane of the movable element for undergoing angular vibrating movement around said axis of vibration towards and away from said fixed element,
• first and second position sensors spaced at different distances from said axis of vibration for measuring distance of said movable element from said fixed element as said movable element undergoes vibration around said axis, the first and second sensors respectively including sensor elements supported at different levels on said movable element so that as the movable element vibrates the sensor elements of the first and second sensors are at equal distances from the fixed element for one particular angular position of the movable element in each half wave of the vibration thereof and are at different distances from the fixed element at all other angular positions of the movable element during said vibration thereof,
• a comparator for comparing distance measurements of the sensor elements to determine a threshold value at which the distance measurements are equal and the movable element is at said one angular position in each half wave of vibration, and
• a device for determining amplitude and/or frequency of vibration of the movable element from said threshold value, independently of the distance of the movable element from the fixed element.